Semiconductor devices and methods of manufacturing the same

ABSTRACT

An example method for fabricating a semiconductor device includes forming a well, a source region, and a drain region in a substrate, forming a gate oxide film on the substrate and coating a polysilicon film on the gate oxide film. Further, the example method includes forming a trench isolation in the substrate by a dry etching process, forming a oxide film on the inside surface of the trench isolation, providing a dielectric material to fill in the trench isolation, planarizing the dielectric material to expose the top surface of the polysilicon film, and forming a gate by dry etching the polysilicon film.

TECHNICAL FIELD

The present disclosure relates to semiconductors and, more particularly,to semiconductor devices and methods of manufacturing the same.

BACKGROUND

Recently, as semiconductor devices have become highly integrated, it isdesirable to have excellent characteristics in a small area in processesfor isolating unit elements. This requires a decrease in the number ofdefects, the use of a good quality gate oxide film, and a development oftechniques for isolating the element.

FIGS. 1A to 1D illustrate cross sectional views sequentially showing aconventional process of fabricating a semiconductor device. As shown inthe drawings, after a hard mask material is coated on a wafer 10 to forma hard mask layer 11, a photoresist pattern 12 is formed on the hardmask layer 11. Following the application of the photoresist pattern 12,a mask for forming a trench isolation is formed by a dry etchingprocess.

Next, the photoresist pattern 12 is removed, and a trench isolation 14is formed by another dry etching process. Thereafter, an oxide film (notshown) is coated on the inside surface of the trench by an oxide filmforming process.

The trench is then filled with a dielectric material, wherein the oxidefilm is coated thereon. By a Chemical Mechanical Polishing (CMP)process, an upper part of the dielectric material and the hard masklayer 11 are planarized until the hard mask layer 11 is removed. Acleaning process is then performed to eliminate entirely any hard maskmaterial remaining on the wafer. Then, a well 17, a source region 15 anda drain region 16 are formed by a photoresist process and an ionimplantation process, and finally a gate oxide film is formed. At thistime, by many processes performed previously, especially the cleaningprocess, a divot 19 is generated.

After a polysilicon layer is coated on the entire wafer, a gate 21 isformed by a photoresist process and a dry etching process.

However, in such fabricating method described above, a poly residue orpoly stringer 20 is produced due to the divot 19. The presence of thepoly stringer 20 deteriorates the operational characteristics andreliability of the semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1D illustrate cross sectional views sequentially showing aconventional method of fabricating a semiconductor device; and

FIGS. 2A to 2E depict cross sectional views sequentially showing aexample method of fabricating a semiconductor device in accordance withone example disclosed herein.

DETAILED DESCRIPTION

Examples of the disclosed methods and devices will now be described indetail with reference to the accompanying drawings, wherein likereference numerals appearing in the drawings represent like parts.

As shown in FIGS. 2A to 2E, a source region 31, a drain region 32, and awell 33 are formed in a semiconductor wafer 30 by a photoresist processand an ion implantation process. After a cleaning process is performed,a gate oxide film 34 is formed on the wafer 30 (FIG. 2A).

A polysilicon film 35 is coated on the gate oxide film 34 and a firstphotoresist pattern 36 for forming a trench is formed on the polysiliconfilm 35 (FIG. 2B).

A trench isolation 38 may be formed in the wafer 30 by a dry etchingprocess using the photoresist pattern 36 as a mask (FIG. 2C).

An oxide film is coated on the inside surface of the trench isolation38, and a dielectric material 40 is provided to fill in the trenchisolation 38. The dielectric material 40 is then planarized to exposethe top surface of the polysilicon film 35 by a CMP process (FIG. 2D).

A second photoresist pattern 37 is formed on the polysilicon film 35 bya photoresist process and a gate 41 is formed by dry etching thepolysilicon film 35 using the second photoresist pattern 37 as a mask(FIG. 2E).

The gate 41 is formed by a two-step dry etching process including afirst etching process without any selective ratio to the dielectricmaterial, and a second etching process with a selective ratio to thedielectric material; and, therefore, the dielectric material 40 in thetrench isolation 38 is not protruded from the gate oxide film 34.

According to the disclosed example methods described above, there isprovided a semiconductor device including the well 33, the source region31 and the drain region 32 formed in the semiconductor wafer 30, thegate oxide film 34 formed on the wafer, the gate 41 formed on the gateoxide film, and the trench isolation 38 in which the dielectric materialis filled.

According to the present disclosure, the number of processes before theformation of the gate oxide film 34 is reduced and, therefore, a pittingphenomenon of the wafer 30 due to wafer damages and defects isdecreased, thereby improving a reliability of the gate oxide film 34 andelectrical and operational characteristics of the device.

Further, no divot is formed at the edge of the trench so that a polyresidue or poly stringer 20 is not produced, thereby increasing areliability of the gate oxide film and decreasing defects to improve theoperating characteristics of the semiconductor device.

Although certain apparatus and methods are disclosed herein, the scopeof coverage of this patent is not limited thereto. On the contrary, thispatent covers every apparatus, method, and article of manufacture fairlyfalling within the scope of the appended claims either literally orunder the doctrine of equivalents.

1. A method for fabricating a semiconductor device comprising: forming awell, a source region, and a drain region in a substrate; forming a gateoxide film on the substrate; depositing a polysilicon film on the gateoxide film; forming a trench isolation in the substrate by a dry etchingprocess; forming an oxide film on the inside surface of the trenchisolation; providing a dielectric material to fill in the trenchisolation and planarizing the dielectric material to expose the topsurface of the polysilicon film; and forming a gate by dry etching thepolysilicon film.
 2. The method of claim 1, wherein forming a gate bydry etching the polysilicon film includes a first etching processwithout a selective ratio to the dielectric material and a secondetching process with a selective ratio to the dielectric material, sothat the dielectric material in the trench isolation is not protrudedfrom the gate oxide film.
 3. The method of claim 1, wherein in thetrench isolation forming, the dry etching process is performed by usinga photoresist pattern formed on the polysilicon film as a mask.
 4. Themethod of claim 1, wherein the planarizing of the dielectric material isperformed by a CMP process.